The Federal Opposition says the Government has to take pressure off interest rates by cutting back on spending.

There have been reports the Government will reveal some savings measures when it releases the mid-year budget update.

Coalition finance spokesman Andrew Robb says the latest interest rate rise shows the Government has lost control of spending.

He says the Government should turn the update into a mini-budget and make some heavy cuts.

"The Government will be totally negligent if it ignores this latest signal," he said.

"In many ways the Reserve Bank is being left to do all the heavy lifting when cutting some of the reckless spending would take pressure off interest rate rises.

"They're addicted to taxing and borrowing and spending, they have to get away from that addiction so they can take pressure off interest rates and look after the livelihoods and peace of mind of families and small business all over this country."

Both sides of politics have attacked the Commonwealth Bank for lifting its variable home loan rate by almost double the Reserve Bank's official increase.

Growing rage over banks and interest rates has moved Mr Swan to strengthen his threats against the big four.

A day after the Commonwealth Bank announced its rate rise, Westpac rubbed salt into the wound by revealing a $6.3 billion profit - an 84 per cent increase on last year's result.

Treasurer Wayne Swan says the Government has been working on several reforms, to boost banking industry competition, that he will reveal next month.

The Treasurer said today that the "arrogant" banks should not underestimate the Government's determination to rein them in.

"The behaviour of the Commonwealth Bank has been arrogant in the extreme," he said.

"So what the Government will do in response to this very arrogant action from the Commonwealth Bank is put in place a further raft of reforms that empower consumers and make sure we get the most competitive outcomes, and that's what we're going to do.

"The ACCC has made it very clear there is a case for additional powers in the area of price signalling. We are working on a raft of reforms."